Twelve million people in the US have diagnosed chronic obstructive pulmonary disease (COPD). COPD is the fourth leading cause of death in the US and is responsible for more than 130,000 deaths annually. At least 15% of COPD cases are attributable to occupational exposures; however, relatively little is known about specific occupational exposure agents that increase the risk of COPD or interactions of occupational exposures and other risk factors such as cigarette smoking. We propose to conduct a case-control study of COPD among construction and craft workers identified at high risk of COPD through preliminary studies. The study includes a broad spectrum of construction crafts with numerous and varied exposures to occupational agents of interest. This study will include approximately 1500 COPD cases and 1500 grouped-matched controls selected from a population of over 15,000 workers undergoing occupational medicine examinations provided by the Building Trades National Medical Screening Program (BTMED), supported by the US Department of Energy. Cases and controls will complete a telephone interview to determine all jobs held more than six months, performance of specific tasks in these jobs, and exposures to agents thought to increase COPD. A panel of three experienced industrial hygienists will conduct exposure assessments of jobs and tasks reported by study participants. Detailed analyses will identify exposures that increase COPD risk and evaluate interactions of occupational risk factors with personal factors such as smoking, prior respiratory history, hobby- related exposures, and family history of COPD. Combining data from the BTMED examinations with detailed information on exposures from the interview questionnaire is innovative and provides a unique opportunity to learn more about specific exposures increasing COPD risk. This study addresses many of the limitations of prior studies of COPD and occupation including: 1) low statistical power due to small populations with low numbers of COPD cases, 2) COPD cases not based on spirometry, 3) exposure assessments often simply based on job title, occupation, or industry, and 4) limited data on non-occupational risk factors such as cigarette smoking, obesity, medical history, family history, and hobby-related activities. The research team is comprised of experienced occupational lung disease researchers with a long history of productive collaboration.